1. Field of the Invention
This invention is in the field of lightweight steel shafts for golf clubs, and golfs clubs having lighter heads made possible by the use of the improved shaft.
2. Description of the Prior Art
In recent years, there has been a significant trend toward the use of lightweight shafts and lightweight heads in golf clubs. The theory behind the lightweight club is that a lighter club at the same swing weight can be swung at a higher velocity for the same amount of swing energy, thereby transferring more momentum to the ball. It is an accepted fact that an increase in clubhead mass or an increase in clubhead velocity will cause an increase in ball velocity. The impact of the clubhead with the ball is governed by the equation: ##EQU1## WHERE Vc=clubhead velocity before impact
Vb=ball velocity after impact PA1 E=coefficient of restitution PA1 Wc=weight of the clubhead PA1 Wb=weight of the ball
All other things being equal, the ball velocity determines the distance the ball will travel. From Equation 1, the distance the ball will travel is inversely proportional to the weight of the clubhead plus the weight of the ball. This means that any change in clubhead weight will have only a small change in the distance the ball will travel. Again using Equation 1, the distance the ball will travel is directly proportional to the clubhead velocity. This means that any change in clubhead velocity will significantly change the distance the ball will travel.
Clubs have recently come on the market utilizing a composite shaft of graphite fibers in a synthetic resin matrix. Such shafts commonly weigh only about 2.5 ounces (70.75 g). While this represents a substantial improvement over a conventional steel shaft which may weigh 4 ounces (113.2 g), the cost of the shaft is sufficiently high so that it is out of the reach of the average player. Player acceptance of these shafts has been low since the feel is much different than steel shafts and the torsional resistance of the shaft causes clubhead rotation during the swing which causes inaccurate shots.